A recording medium conveying device for an image forming apparatus of the present invention includes a conveying member for conveying a sheet or similar recording medium by nipping it. After the sheet being conveyed by the conveying member has abutted against a registering member, the registering member rotates in synchronism with the rotation of an image carrier carrying an image thereon for thereby conveying the recording medium toward an image transfer position. After the recording medium has slackened on abutting against the registering member, a nip canceling mechanism cancels the nip of the conveying member acting on the recording medium.